<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
    /* 伪元素-->用css自定义生产的元素
    div:before{
        content:""
        }
     */
    div:before{
        width:100px;
        height: 100px;
        background: red;
        content:"前面";
        display:block;
    }
    div:after{
        content:"后面";
        display:  block;
        width: 100px;
        height: 50px;
        background: yellow;
    }
    </style>
</head>
<body>
    <div>
        content
    </div>
</body>
</html>